A key structure which is capable of giving a woody appearance to the key, and increasing the freedom of mounting at least one functional part formed as a separate part from the key structure, while maintaining excellent machinability. An upper plate has an increased width part corresponding to an end of a white key toward a player. In the key structure, a wood part is secured to the lower surface of at least the increased width part of the upper plate, and has an increased width part having substantially the same width as the increased width part of the upper plate. The key structure is mountable in a keyboard apparatus, for functioning as a white key pivotally moved by key-depressing operation. A recess is formed in a part of the wood part including the increased width part, which opens downward and has a width (W0) not less than 50% and not more than 80% of the width (B0) of the increased width part of the wood part.